1. Field of the Invention
The present invention generally relates to an automatic ice making or manufacturing apparatus, and more particularly to an automatic ice manufacturing apparatus having a structure capable of suppressing increase in the concentration of impurities contained in ice making water (i.e. raw water to be iced) stored in a raw water tank.
2. Description of the Prior Art
Referring to FIG. 3, there is schematically shown a typical structure of the automatic ice manufacturing machine known heretofore in the art, wherein a reference numeral 1 denotes an ice making unit which is composed of an ice forming plate 2 and an evaporator tube 3 mounted on the rear surface of the ice forming plate 2 in a meandering pattern. Disposed above the ice making unit 1 is a first water spray or distribution tube 4 which is provided with an array of water spray orifices 4a for distributing water over the front surface of the ice forming plate 2, which water then flows downwardly over and along the plate 2. The first water spray tube 4 is connected to a water tank 6 storing raw water (i.e. water used for making ice) by way of a water circulating conduit 5 in which a circulating pump 7 is provided for circulating water between the water tank 6 and the ice making unit 1 through the circulating conduit 5.
Further disposed above the ice making unit 1 is a second water spray tube 8 having formed therein a row of plural water spray orifices 8a for spraying water onto the rear surface of the ice forming plate 2, the water as sprayed flowing therealong downwardly under gravity. This second water spray tube 8 is connected to a raw water supply source (not shown) through a water supply pipe 9 which is equipped at an intermediate portion thereof with a water valve 10 adapted to be opened during a deicing (ice removing) cycle for supplying water to be sprayed over the rear surface of the ice forming plate 2.
Installed between the ice making unit 1 and the water tank 6 is an inclined ice guide plate 11, in which a plurality of dewatering holes 11a are formed. An overflow pipe 12 upstanding vertically is fixedly mounted on the bottom of the water tank 6, extending therethrough downwardly, and serves for controlling the highest water level within the water tank 6. A sub-tank 14 having a float switch 13 mounted therein is hydraulically communicated with the water tank 6.
Operation of the automatic ice manufacturing machine of the above structure described will be explained. During an ice making cycle (also referred to as the icing cycle), a refrigerating system (not shown) is operated to supply a coolant of low temperature and low pressure to the evaporator tube 3, whereby the ice forming plate 2 is cooled down. Additionally, the water circulating pump 7 is operated to circulate water between the ice forming plate 2 and the water tank 6. Water is refrigerated in the course of flowing downwardly along and over the front surface of the ice forming plate 2, resulting in that ice grows progressively on the plate 2, which is accompanied with corresponding lowering of the water level within the tank 6. When the ice has grown to a predetermined thickness on the ice forming plate 2 with the water level within the tank 6 also having been lowered to a predetermined level, the float switch 13 detects this level and produces a corresponding output signal which is applied to a control apparatus (not shown), whereby the operation of the water circulating pump 7 is stopped while the water valve 10 is opened under the command of the control apparatus. Thus, the icing operation cycle comes to the end, being followed by the start of an ice removing cycle (also referred to as the deicing operation cycle).
When the water valve 10 is opened at the start of the deicing operation cycle, raw water supplied through the pipe 9 from the water source (not shown) is sprayed over the rear surface of the ice forming plate 2 from the second water spray tube 8 and flows downwardly to be stored within the water tank 6 through the dewatering holes 11a. During the flowing of water along the rear surface of the ice forming plate 2, ice formed thereon is partially defrozen at a portion contacting the ice forming plate 2 after lapse of a time due to the heat exchange between the water and a medium of a high pressure and a high temperature which is caused to flow through the evaporator tube 3 simultaneousy with the opening if the water valve 10. Ice is thus removed from the ice forming plate 2 and drops onto the inclined guide plate 11 to be ultimately stored in an ice storing chamber (not shown). In the course of the deicing cycle, the water level within the tank 6 reaches the open upper end 12a of the overflow pipe 12. Thereafter, water flowing into the tank 6 is drained outwardly through the overflow pipe 12.
In succession to the removal of ice from the ice forming plate 2, the temperature of the evaporator tube 3 increases to a predetermined point, which is detected by a deicing temperature sensor (not shown) mounted on the evaporator tube 3. In response to the output signal of the sensor, the water valve 10 is closed, while the operation of the water circulating pump 7 is restarted with the coolant of low temperature and low pressure being again fed through the evaporator tube 3. In other words, the deicing cycle is completed and the icing cycle described previously is initiated again.
In the automatic ice manufacturing machine of the structure described above, it is observed that repetition of the icing cycle brings about progressive increase in the concentration of impurities contained in raw water the water tank 6. In case the impurity concentration of raw water supplied through the pipe 9 is high, sediments such as calcium and other will be deposited on the bottom of the water tank 6, and sometimes the water spray orifices 4a of the first spray tube 4 are blocked or closed, presenting an obstacle to the normal icing operation and/or involving deterioration in the quality of ice as manufactured.